T. vasslievi (BenaMolaei et al. 2018c), while that of the O. fecundus was very longer
(11.4–14.3 with an average of 12.7 min; Iranipour et al. 2013a). In addition, the
maximum attack rate was 42–48 in T. vassilievi and < 21 in O. fecundus. This may
imply that total time of 2.5 and 4.5 h is adequate for a complete daily clutch by those
species respectively. Considering further time will increase handling time estimates
unrealistically. In similar 6 h lasted experiments, the higher slope of searching
efficiency (parameter b of the type III functional response) in T. vassilievi compared
to T. djadetshkoe (Abdi et al. 2015) shows a stronger density-dependent response of
the former. In addition, the constant value of searching efficiency in type II response
of T. grandis and O. telenomicida imply that these species find host eggs more
rapidly than T. djadetshkoe in densities below 4–8 host eggs whereas in higher
densities the status is the reverse. This suggests an advantage of type III response in
higher densities.
8.5.1.3 Effect on Thermal Requirements
Thermal requirements may determine distribution range of a species, can use for
predicting the result of competition in different climates and estimate species
evenness in a guild. In a few studies, the thermal requirements of Trissolcus spp.
were studied. Safavi (1973) suggests that species with parapsidal grooves have
overall longer development time than those one lacking them. This statement
confirmed by later works (see discussion by Iranipour et al. 2015). As an instant,
T. brochymenae has the longest development among Trissolcus species (214.7 DD;
Torres et al. 1997; Cividanes et al. 1998). Furthermore, the shortest one recorded for
T. rufiventris (125.0 and 111.1 DD for females and males respectively; Kivan and
Kiliç 2006b). Comparison between T. vassilievi (Iranipour et al. 2015) and
T. grandis (Iranipour et al. 2010) also show 10–40% lower DD for the latter. In
both cases, two populations were studied simultaneously. Despite the closer distance, T. grandis populations showed larger differences. Two degrees Celsius
difference in thermal threshold (12.5 vs. 14.5
C) and 27–38 DD in thermal constant
(116.9 vs. 143.8 in males and 124.6 vs. 162.9 DD in females) was observed in
T. grandis. Similar statistics for T. vassilievi was 13.0–13.8
C and 12.2–12.6
C for
the threshold and 192.2–204.2 and 164.0–173.9 for thermal constant of females and
males respectively. The authors concluded that higher phenotypic plasticity in
T. grandis enables it to develop in wider ranges and adapt to colder regions.
8.5.2 Effect of External Factors – I. Biotic Factors
Host Plant
Host plant mainly affects sunn pest itself, but some indirect effects may be expected.
For example, often barley is more developed when parasitoids and hosts come in
fields. It may attract a higher number of them and cause density-dependence effects.
8 Superfamily Platygastroidea: Natural Enemies of True Bugs, Moths, Other. . .
317
(11.4–14.3 with an average of 12.7 min; Iranipour et al. 2013a). In addition, the
maximum attack rate was 42–48 in T. vassilievi and < 21 in O. fecundus. This may
imply that total time of 2.5 and 4.5 h is adequate for a complete daily clutch by those
species respectively. Considering further time will increase handling time estimates
unrealistically. In similar 6 h lasted experiments, the higher slope of searching
efficiency (parameter b of the type III functional response) in T. vassilievi compared
to T. djadetshkoe (Abdi et al. 2015) shows a stronger density-dependent response of
the former. In addition, the constant value of searching efficiency in type II response
of T. grandis and O. telenomicida imply that these species find host eggs more
rapidly than T. djadetshkoe in densities below 4–8 host eggs whereas in higher
densities the status is the reverse. This suggests an advantage of type III response in
higher densities.
8.5.1.3 Effect on Thermal Requirements
Thermal requirements may determine distribution range of a species, can use for
predicting the result of competition in different climates and estimate species
evenness in a guild. In a few studies, the thermal requirements of Trissolcus spp.
were studied. Safavi (1973) suggests that species with parapsidal grooves have
overall longer development time than those one lacking them. This statement
confirmed by later works (see discussion by Iranipour et al. 2015). As an instant,
T. brochymenae has the longest development among Trissolcus species (214.7 DD;
Torres et al. 1997; Cividanes et al. 1998). Furthermore, the shortest one recorded for
T. rufiventris (125.0 and 111.1 DD for females and males respectively; Kivan and
Kiliç 2006b). Comparison between T. vassilievi (Iranipour et al. 2015) and
T. grandis (Iranipour et al. 2010) also show 10–40% lower DD for the latter. In
both cases, two populations were studied simultaneously. Despite the closer distance, T. grandis populations showed larger differences. Two degrees Celsius
difference in thermal threshold (12.5 vs. 14.5
C) and 27–38 DD in thermal constant
(116.9 vs. 143.8 in males and 124.6 vs. 162.9 DD in females) was observed in
T. grandis. Similar statistics for T. vassilievi was 13.0–13.8
C and 12.2–12.6
C for
the threshold and 192.2–204.2 and 164.0–173.9 for thermal constant of females and
males respectively. The authors concluded that higher phenotypic plasticity in
T. grandis enables it to develop in wider ranges and adapt to colder regions.
8.5.2 Effect of External Factors – I. Biotic Factors
Host Plant
Host plant mainly affects sunn pest itself, but some indirect effects may be expected.
For example, often barley is more developed when parasitoids and hosts come in
fields. It may attract a higher number of them and cause density-dependence effects.
8 Superfamily Platygastroidea: Natural Enemies of True Bugs, Moths, Other. . .
317